They send to you a notice after three monthly defaults after which, litigation starts.
The procedure in Courts needs to be duly notified to you at the address you agreed as relevant for notifications on the mortgage deed.
This notification enables you to deffend your position that, even when limited for this type of procedures ( recently enlarged due to European requirements), is still possible.
I always advise clients to answer the repossession with a dation counteroffer in order to reach an agreement with the bank to have the whole debt settled after the auction. Of course the difficulty of this varies depending on the equity you have on the house.
As you know the way the Bank has to obtain liquid value out of the house is through public auction after which, if no one bids, the bank can keep it for no lower than 70% of the price ( for first residences) and 50% ( for second residencies) that the house when it was valuated for mortgage purposes ( this value is contained in mortgage deds and it is the sum of borrowed capital+ interests+ legal expenses)
Never leave a repossession order unattended as there is also the risk of the Bank applying for the issuing of an european enforcement order against your assets in the UK.
Please let me know if you have further questions,